The present invention relates to a wire bonding method of carrying out wire bonding between a semiconductor chip and a package, and more particularly to a method to apply wire bonding to an elongated semiconductor chip such as, for example, a solid state image pick-up device.
A semiconductor chip used in a solid state image pick-up device is of an elongated structure such that the width is 1 mm whereas the length is 30 to 100 mm. A plurality of bonding pads serving as electrodes of such an elongated semiconductor chip are arranged along its length direction in a column manner. Accordingly, the bonding range required for applying wire bonding to such bonding pads thus arranged in a broad range is broader than the bonding range in an ordinary semiconductor chip. For this reason, the special bonding methods described below have been conventionally applied.
(1) Selecting the central portion in the length direction of a semiconductor chip as a branch point, bonding pads arranged on one side of the branch point are first subjected to bonding using a wire bonder. Then, half turn of the semiconductor chip is made with the branch point being as center to apply bonding to bonding pads arranged on the opposite side of the branch point using the wire bonder. This method is particularly applied to the ultrasonic bonding.
(2) A semiconductor chip is intermittently moved with respect to a wire bonder. Thus, wire bonding is successively applied at respective movement positions.
(3) A plurality of wire bonders are disposed along the length direction of a semiconductor chip to carry out bonding using respective wire bonders.
However, the above-mentioned method (1) requires positional accuracy when rotating the semiconductor chip. Particularly, where bonding pads are formed at the end portion in the length direction of the semiconductor chip, it is required to maintain accuracy at the end point. For this reason, it is necessary to calculate coordinates of the bonding position. In addition, movement stroke of an X-Y table on which the wire bonder is mounted becomes large, with the result that the wire bonder becomes large-sized. On the other hand, the above-mentioned method (2) requires positioning of the semiconductor chip every time the semiconductor chip is intermittently moved, resulting in prolonged loss time and troublesome operation. Further, the last-mentioned method (3) requires a large number of wire bonders, so that the entirety of the wire bonding apparatus becomes complicated and the cost therefor is increased.